JPH0711396B2 - Molten metal agitator - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention is an improved molten metal stirring device, and in particular for stirring molten metal in a furnace in which the metal is melted or alloyed, for example molten aluminum. Related equipment.

PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION There is a desire for rapid and effective agitation of the contents of a bath of molten metal, but efforts have been made to develop new methods and apparatus to achieve such objectives. It has been done quite a bit. Such a technique is such that a metal is first melted, a solid metal is added to the already melted melt, the added metal is melted, an additive such as another metal is introduced, and alloying is performed, and further fine grains are added. It facilitates the operation of chemical conversion and improves the temperature control to facilitate maintaining the metal body at a uniform temperature and composition. Moreover, such a technique can significantly reduce the energy required to melt the metal and hold it in the molten state.

With the development of various metals, especially aluminum alloys, which must be agitated to homogenize the alloy composition and temperature before pouring, effective agitation becomes more important. One of the widely used systems in aluminum furnaces is to use a tool attached to the end of a boom mounted on a lift truck, where the agitation is
This is done by moving the tool back and forth in the melt. This system has the drawback of applying a mechanical shock to the refractory lining, as well as the metal surface being agitated resulting in the formation of dross and, in addition, the furnace to accommodate a stirring tool during this operation. The door has to be opened, which has the disadvantage of increasing heat loss.

Another method used is to inject the gas under pressure through the melt through one or more lances, but this method has the disadvantage of increasing the formation of dross and the erosion of the refractory lining. is there. The furnaces mainly used for aluminum are less efficient than mechanical agitation due to their wide and shallow limits on the working range of the lances, and therefore the use of multiple lances or bathing of lances. It will be necessary to move along the perimeter of.

Two different types of electrical systems have also been developed: electromagnetic stirrers and mechanical or electromagnetic immersion pumps. The magnetic stirrer is arranged below the furnace and is equipped with a large induction coil that produces an electromagnetic stirrer in the metal. Such a stirrer has the advantages of being applicable to any type of furnace, being efficient and having no elements in direct contact with the metal. However, this stirrer is relatively expensive, and in 1988, about 60,000 to 850,0
It is estimated to be US $ 00. Immersion pumps are compact devices that are submerged in metal in an access well and are therefore primarily limited to furnaces with such a reservoir. Although this pump is significantly less expensive, it is subject to the harsh operating conditions of being immersed in metal, requiring constant maintenance.

Another mechanical system, commonly referred to as a jet pump, is also under development, which comprises a tube forming a tubular reservoir connected to the furnace, with a portion of the molten metal in the tube. Vacuum suction, then gas pressure and / or
Or it is forced back into the bath by gravity. By choosing appropriate parameters such as nozzle diameter and initial metal velocity, the intermittent jet (intermi-
It can be agitated with the whole furnace within a few minutes after the start of the operation.

For example, in connection with the inventions of Fitzpatrick and others, Alcan Research and Development Limi
U.S. Pat. No. 4,008,884 assigned to Ted) discloses such an intermittent jet agitator. This device is installed at approximately 40 to 50 vertically through one side wall of the melting furnace.
It comprises a cast iron pipe or tube extending downwards at an angle of degrees, terminating in a nozzle which is close to the hearth and is oriented horizontally longitudinally towards the other side wall.
A pneumatic ejector is connected to the top of the pipe and operated at regular intervals to create the vacuum necessary to draw the molten metal into the pipe until it is above the bath level. When the liquid level reaches the upper limit, the vacuum is released and air is introduced under pressure, introducing the metal through the nozzle into the bath in the form of a high-speed jet. For a furnace of about 40-50 tons, the patent proposes to use a tube with an inner cross-sectional area of about 738 square centimeters (45 square inches) and a length of 3 meters (9 feet), This allows the tube to be approximately 90-115 kilograms (200-25
0 pounds) can be emitted and the metal has a diameter
Approximately 32Kmph (20mp through a 3.8cm (1.5 inch) nozzle
Exit at the speed of h). Approximately 6 to 7 in the suction process of the cycle
It takes seconds, the pressure step takes only about 0.5 to 1 second, and the air pressure is 1.4 to 2.8 kg / cm ² (20 to 60 psi).

A similar type of device that uses a tube that is inserted from the side and tilted upward has been described, for example, in U.S. Patent No. 3,599,831.
No. 4,235,626, 4,236,917, 4,355,78
No. 9 and No. 4,463,935, British Patent Application Publication No. 2,039,
761A and 2,039,765A, and Japanese Patent Application Nos. 1983-136982 and 1984-70200.

U.S. Pat. No. 3,424,186 discloses a circulator with a vertical wall which consists of a hollow chamber located in the side reservoir of a furnace and which divides the interior of the chamber into two parts. A vacuum device at the top of the chamber, until the metal flows over the top of the wall,
Simultaneously withdraw from the furnace and reservoir via their respective mouths. The port leading to the furnace is much larger than the port leading to the sump,
Although the metal is allowed to flow faster, the chamber portion on the side of the wall supplied by the bath is significantly larger, allowing the metal to be transferred from the furnace side of the wall to the sump side. The metal is passed through the usual mouth that connects the sump and the furnace,
It flows from the reservoir to the furnace.

Another type of stirrer is disclosed, for example, in U.S. Pat.Nos. 4,427,44 and 4,452,634, wherein the stirrer is located above the bath and has a lower end that reaches into the metal. With a pipe extending in the direction, the metal is drawn into the pipe by vacuum and returned by gravity.

Although these prior art devices can provide effective agitation, they create a number of problems in operation. For example,
Since the lower part of the tube used is in direct contact with the molten metal, it immediately causes erosion. The middle section is above the molten metal, but at high burner temperatures (eg 1000 to
Since it is still located inside the furnace exposed to 1100 ° C), the material of the tube (eg cast iron) deteriorates,
The system may become inoperable or costly to activate. Moreover, for relatively small diameter pipes, it is difficult to provide a thick insulating layer, and unless the tube is provided with an internal heater embedded in the wall as disclosed, for example, in U.S. Pat.No. 4,463,935. , Deposits of solidified metal and oxides at a fast rate on the inside of the wall in the form of a plaque ring or brim. In extreme cases, when the temperature drops near the melting point,
The metal in the tube may solidify, or at least become significantly more viscous. Even if the heater is installed, if the erosion of the pipe wall cannot be avoided and the molten metal penetrates through the cracks in the lining, the heater is immediately damaged and it is notable to replace it with a pipe having a smooth surface. Difficult and expensive.

Moreover, these systems are very difficult to control the maximum and minimum levels of metal in the tube. In fact, it is not possible to prevent the formation of "dust" rings or brims, especially in the case of magnesium-rich aluminum alloys, which react rapidly with the oxygen contained in the inner wall of the stirrer. U.S. Pat.No. 4,463,935 proposes that the combustion gas from the furnace has a low oxygen content, so that it is used as a propellant gas to prevent the oxidation of the metal in the tube as much as possible. This gas has a high proportion of H ₂ O and will easily oxidize the molten metal at such temperatures.

Due to the small diameter of the tube, a very small amount of dirt ring is large enough to come into contact with the electrodes used to control the upper level and cause a short circuit, rendering the controller inoperable. If the top level cannot be controlled, the metal will immediately fill the top of the tube and solidify in the pneumatic element, causing the entire system to stop irreparably. In addition, a small ring is created quickly,
The inside must be cleaned at all times, but cleaning with smaller diameter tubes is difficult and more costly to maintain. If the upper level control is not working or is not working properly, the lower level control will not work properly, and therefore, when the metal level drops below the lower level, some of the propellant gas will be transferred to the furnace and pipe. It will enter the molten metal through the orifice between and. This can be avoided in systems that rely solely on gravity for the release of metal, but entrain another metal (entr
ain) and it is difficult to obtain a sufficiently high velocity jet of metal, where it is desirable to have the stirred jet reach the entire area of the bath. This phenomenon of injecting gas into a metal bath is known as "bubbling" and, in significant cases, occurs at each cycle of operation, disturbing the metal surface in the furnace, as well as debris and aluminum oxide. Formation is promoted, which further leads to metal loss.

In the device described in the Fitzpatrick et al. Patent, cited above, the metal jet means are mounted in one wall and directed towards the opposing wall. In another system, such as that disclosed in U.S. Pat. Nos. 4,235,626 and 4,236,917, the jets are directed to the bottom of the furnace, which reduces agitation efficiency and increases refractory lining erosion.

Since most of the prior art systems described above form an opening between the pipe and the interior of the furnace that is approximately the same size as the inside diameter of the tube, the resulting exit velocity will necessarily result in a smaller diameter orifice. It is much smaller than what would be obtained if used and the amount of metal transferred and the stirring strength are reduced. In order to compensate for this, in the system disclosed in U.S. Pat.No. 4,235,626, it has been proposed to move the tube during operation to provide a larger agitation area, but with a complicated mechanical structure, Maintenance becomes difficult in the harsh environment of the furnace and the relatively high moving speed.

Thus, stirring does not disturb the bath surface of the furnace and does not open the loading door or shut down the furnace burner.
Moreover, it can be seen that it must be possible to mix the contents of the bath completely and quickly without the need for any equipment treatment when the stirring process is started. According to such an apparatus, since the stirring is performed under the bath surface, the formation of dross can be prevented as much as possible, and therefore, the thermal gradient of the bath can be removed, so that the temperature can be controlled well. At the same time, it is possible to reduce the oxidation on the surface caused by the decrease in the temperature of the bath surface. Further, the alloy components can be more efficiently melted and the heat transfer is favorably performed, so that the remelting rate can be increased and the energy consumption can be reduced. Both of these are preferably accomplished by a device that allows both installation costs and subsequent maintenance costs to be as low as possible.

Therefore, it is an object of the present invention to provide a new stirring device for stirring molten metal.

An object of the present invention is to provide a system and an apparatus capable of satisfying the requirements regarding cost and maintenance cost and efficiently performing agitation.

(Means for Solving the Problem) According to the present invention, there is provided a stirring device for stirring the molten metal in the furnace chamber. This agitator has a reservoir chamber separated from the furnace chamber, a passage for communicating molten metal between the inside of the furnace chamber and the reservoir chamber, and for introducing molten metal from the furnace chamber into the reservoir. Vacuum / pressure connected to the interior of the sump chamber to alternately and continuously form a vacuum in the chamber and a positive pressure for discharging the molten metal from the reservoir into the furnace chamber in the form of a stirred jet And generating means.

In such a device, the passage is provided with a nozzle, the ratio of the cross-sectional area of the nozzle to the horizontal cross-sectional area of the interior of the sump being in the range 1:50 to 1: 250, preferably 1:60 to 1: 150.

The ratio of the horizontal cross-sectional area inside the sump chamber to the vertical distance between the upper and lower levels can be about 1:10 to 1:20 and is 25 cm ² / cm (10 square inches / Inches) or more.

The ratio of the diameter of the horizontal cross section inside the sump chamber to the vertical distance between the upper and lower levels is about 1.0: 1 to 2.
It can be 0: 1.

Alternatively or additionally, the sump chamber may include a removable cover portion for providing access to the interior of the chamber, the cover portion heating therein the interior of the sump chamber and the molten metal therein. It is equipped with a heating means.

Preferably, the interior of the reservoir is substantially circular in horizontal cross section,
The passage is horizontally opened tangentially to the circular cross section, and the molten metal passing through the passage is discharged substantially horizontally and tangentially to the circular cross section, so that the molten metal entering the reservoir is stored inside the reservoir. The vortex is formed at.

Preferably, the removable cover part also comprises a detector for detecting bubbling of the pressurized gas introduced into the furnace from within the reservoir.

Preferably, the butterfly valve is controlled based on the output of the level control electrode for detecting the upper level of the molten metal and the pressure detector for detecting the bubbling, and the butterfly valve periodically switches between positive pressure and vacuum to store the inside of the reservoir chamber. It is designed to be applied to.

The sump chamber can weigh the sump chamber to measure the level of molten metal in the sump chamber, and / or
It can be mounted on a metering device that can detect foaming of the pressurized gas introduced from the inside of the reservoir to the inside of the furnace.

Preferably, the passageway is 10 at one end of the furnace adjacent to one side or at one side of the furnace adjacent to the open end with respect to the face of the open end.
It extends to the furnace at an angle of ~ 45 degrees.

EXAMPLES The present invention will now be described with reference to the examples shown in the accompanying drawings, which are described below with reference to the general reference numeral 10 for shallow planar aluminum melting or casting. It is designed to be used with a furnace. Furnace 10
Includes hearth 12, end walls 14 and 16 and side walls 18 and 20.
And inspection doors 22 provided at various places and a loading door 24 provided along the side wall. The stirrer is indicated generally by the reference numeral 26 and is disposed along the side wall 20, close to the junction of the side wall 20 and the end wall 24.
The stirrer 26 is provided with a nozzle portion 27 for putting molten metal in and out of the furnace, the molten metal being drawn from the furnace through the stirrer 26, and a surface parallel to the surface of the end wall 15. By returning to the furnace at an angle A of about 10 to 40 degrees with respect to the furnace, the jet of metal entering the bath is directed at an angle corresponding to the other side wall 18 but towards the other end wall 16. Also has. If the jets are directed to the opposite side walls at a smaller angle A, the agitation cannot be performed well and the erosion of the refractory lining is likely to occur. There are numerous alternative locations suitable for placement of the stirrer, two of which are shown in dotted lines in FIG. Such a location is ultimately selected mainly by the location of the space around the furnace, which is suitable for the installation of the device.

2 to 6, the stir chamber of the stirring device of the present invention is completely separate from the furnace used, but as shown in FIGS. The nozzle part is installed in the furnace wall and a short distance above the hearth (usually
At about 15 to 40 cm), it is discharged horizontally into the furnace and turbulent flow is obtained. The jet entrains the metal so that it is performed in most furnaces with a strong molten metal without waviness on the metal surface and without depositing dust on the metal surface.

In the present embodiment, the reservoir is provided with a cylindrical lower case 28 made of a steel plate, the lower end of which is closed and the upper end of which is open, and which is mounted on an appropriate support. In the illustrated embodiment, the case, when placed, is mounted on a load cell 30 that functions as described below. The open upper end is closed by a dome-shaped cover member 32 formed of a cylindrical upper case having the same horizontal diameter,
The two cases have matching annular flanges 34
And 36 are provided and the flanges are clamped to each other as needed by an easily removable pivot bolt 38 or other equivalent clamping device. A normal airtight seal (not shown) is interposed between these flanges.

The cover is supported by the lower case 28, is attached by brackets 40 to vertically extending rods 42 mounted on vertically spaced bushes 44, and can move vertically as indicated by arrow 46. You can do it. Further, the rod 42 is rotatable about a longitudinal axis, as indicated by arrow 48. The rod is movable up and down via a lower end portion by a jack 50 as required, and the jack is operated by an electric motor 51, and the operation of the jack causes the cover to move to an upper portion shown by a dotted line in FIG. Moved up to the position. Alternatively, hydraulic jacks and actuation systems associated therewith can be used. In this upper position, the level detector member suspended from the cover is rotated from the position directly above the reservoir to the removal position indicated by the chain line in FIG.
Lifted high enough to move away from the casting flange. In this removal position, the operator has easy access to the underside of the cover and the interior of the sump. This rotation can be automatically performed at the top of the moving position in the vertical direction by an appropriate driving body (not shown).

The dimensions of the particular embodiments shown may be as shown below, but these and other dimensions should be understood as merely exemplary, unless otherwise limited, and the present invention is not intended to be limited to these. It should not be construed as limiting. In this embodiment, the lower cylindrical case 28 and the outer case forming the cover are made of a steel plate of 10 mm (0.375 inch). The lining to allow the sump to withstand repeated cycles of contact with molten metal is made of an insulating material [sold by Plibrico under the trade name "PLIVAFORM"] 100mm (4b) first outer lining 5
2 and a second intermediate lining 54, which is made of refractory material (sold by the company under the trade name "LW1-28") and has a wall thickness of 125 mm (0.5 inch), and a third that contacts metal. It consists of an outer lining and. The third inner lining 56 is “REF” from Carborundum.
It is formed to a thickness of 50 mm (2 inches) from a carbon fired silicon refractory material such as the material sold under the trade name RAX.
These relatively thick insulating linings minimize heat loss when the metal is inside the sump, while the relatively thick third refractory layer wears due to moving molten metal. Provide a long life inner lining. The furnace is usually thicker but is provided with a similar refractory lining.

Openings are formed in the reservoir sidewalls and linings, and matching openings are formed in the furnace linings and sidewalls. Case 28
And the furnace wall 20 have matching circular flanges 58, respectively.
And 60 are provided and these flanges are connected by bolts 62 to allow the reservoir to be easily removed from the furnace when repairs, linings, etc. are needed. A block 64 molded from silicon carbide or other suitable refractory material is attached to the side walls of the furnace and is surrounded by refractory and insulating material and is specially formed to pass molten metal between the furnace and the interior of the sump. Form a passage. The reservoir side portion 66 of this passage has the same cross-sectional area as the reservoir side wall opening, but the intermediate portion 68 has a significantly smaller diameter,
It constitutes a nozzle that forms a jet of metal as the metal moves in and out of the sump. The furnace side portion 70 tapers outwards towards the interior of the furnace so that the outgoing jet of metal spreads outwards as indicated by arrow 72 in FIG. 6 to maximize ambient bathing. While being carried, the stirring is made more effective. In this embodiment, the block 64 is approximately 46 cm (18 inches) in length, has a portion of the lateral area shown in FIG. 7, and has a circular nozzle opening.
68 has a diameter of 6.5 cm (2.5 inches) and a cross-sectional area of approximately 35 cm ²
(5.0 square inches).

Any of the components in the lower portion of the reservoir of case 28 can be considered to have "static" nature, which typically requires replacement at relatively long intervals. All of the "active" components of the agitator are carried in a removable cover, except for the thermostat 74, which is located on the lower sidewall. The sensing element of the thermostat 74 only penetrates the linings 52 and 54 and is blocked from contact with metal by the inner lining 56, whose control circuit compensates for the lower measured temperature. Is adjusted.

The dome-shaped interior of the cover is made of insulating and refractory material, leaving a central space 76, as clearly shown in FIGS.
It is lined with 75 layers. In this embodiment, three laterally-extending, horizontally extending, silicon carbide, high-temperature rod-type electric heating elements 78 are attached to the cover, and the generated heat is directly or internally reflected. To radiate more. The heater is firmly attached at both ends to minimize damage from vibration, and each end is easily accessible for easy replacement without moving the cover 32. It is attached via the outer case 80. Each case 80 has a removable cover 82. If desired, the heaters can be prevented directly from splashing from the molten metal by their respective horizontal shields 84.

These heaters perform a number of important functions including:

(1) It is possible to preheat the inside of the reservoir before starting or restarting and prevent the metal from solidifying when the metal enters.

(2) Hold the metal remaining in the sump in a molten state when the stirrer is not in use.

(3) The inner wall of the reservoir is at a high enough temperature to minimize the buildup of dirt and to facilitate the removal of dirt (about about 5% for aluminum).
Hold above 700 ° C).

(4) Keep the scale at a temperature high enough to facilitate removal of the scale from the wall at regular intervals. The heater has sufficient rated power to achieve these goals, and
It is operated under the control of the thermostat 74 by a suitable control system.

The cover also mounts three electrodes 86, 88 and 90 which are used to control the upper level inside the reservoir. The two electrodes 86 and 88 consist of a metal rod, the metal of which is the normal upper level indicated by the dash-dotted line 92 in FIG.
el) constitutes a normal upper level detector that is electrically connected when it reaches. The corresponding normal lower level is
It is indicated by a chain double-dashed line 94. Electrode 90 is shorter and, in cooperation with electrode 86, metal level 96
When it reaches, the pneumatic circuit is completely shut off, and
As will be described in detail below, an emergency level detector is constructed that operates to connect the interior of the reservoir to the atmosphere and empty the interior of the reservoir to level 98 where it is flush with the contents of the furnace. The cover further includes a viewing port 100 that allows an operator to inspect the interior and a pilot pressure connection that communicates the pressure in the reservoir obtained through hole 104 with a pneumatic control system for the purposes described below. A body 102 and an inlet / outlet pipe 106 for pumping gas to and from the reservoir are attached. The pipe 106 is closed at its lower end and has holes 108 formed in a radial shape so that gas entering the pipe is not directed to the metal, thereby minimizing splashing of metal and formation of dust, and It is designed to protect the heating element.

A particular pneumatic circuit that activates and controls the system is described. The circuit continuously and alternatively creates positive and negative pressure differences between the interior of the sump and the interior of the furnace so that metal is drawn into and discharged from the interior of the sump. Acts as if it were. Figure 8A shows about 22 /
The "ideal" characteristic of the change in pressure value inside the reservoir during one cycle of operation is shown by the dotted line, and the solid line shows the more usual characteristic obtained. FIG. 8B shows the corresponding variation in metal level. Generally, the high pressure used is
Range of 0.35 to 1.0 kg / cm ² (5 to 14 psi), usually about 0.
70 kg / cm ² (10 psi), low pressure is −0.35 to −
0.70kg / cm ² (-5 to -10psi) range, usually about -0.5
It is 0 kg / cm ² (-7 psi).

Also, typically, the aspirating (vacuum) part of the cycle takes 10 to 15 seconds and the venting (pressure) part takes 10 to 15 seconds, which usually takes about 20 to 30 seconds for the entire cycle. Become. Due to the large size of the reservoir, the function of the stirrer is not limited by design, but mainly by the amount of compressed air delivered, which in turn depends on the size of the device supplying the compressed air. Defined by These parameters define the total time of the cycle and thus the flow rate and velocity of the metal jet.

Although some of the dimensions of the device of this embodiment have been described above,
Further relevant dimensions are:

Case 28 outer diameter = 117 cm (46 inches) Chamber inner diameter = 60.0 cm (24 inches) Internal cross-sectional area = 2830 cm ² (450 square inches) Heater 78 rated output (each) = 8 kw Case 28 height = 168 cm (66 inches) Height including cover 36 = 218 cm (86 inches) Vertical movement of cover = 40 cm (16 inches) Height of levels 92 to 94 = 110 cm (43 inches) Internal volume = 1800 liters (63 cubic feet) Maximum Capacity = 650 kg (1430 lbs) 1 cycle metal mass change = 5
50-600 kg (1200 to 1320 lbs) Nozzle cross-sectional area = 35 cm ² (5.0 square inches) A relatively large amount of metal is moved in one cycle, and a relatively small nozzle cross-sectional area makes it relatively large Velocity jets are obtained and will typically be about 4 to 12 meters / second (800 to 2400 fpm), more typically 6 to 10 meters / second (1200 to 2000 fpm), depending on operating conditions. At a cycle time of 20 seconds, the maximum average total flow is
It is about 1800 kg / min (4000 lbs / min). The amount of metal taken into the furnace is 5 to 15 times the amount coming out of the nozzle,
In the case of a 40 ton furnace, which reaches about 15 percent of the furnace volume per cycle, the furnace is thoroughly stirred within minutes without any noticeable turbulence appearing on the bath surface.

For the operation of the present invention, it is important that the interior of the reservoir has a relatively large horizontal cross section, and from an implementation perspective,
The cross section can be square and rectangular, but is usually cylindrical, with a preferred minimum diameter of 50 cm (20 inches) and a minimum cross-sectional area of 1960 cm ² (314 square inches). The maximum diameter can be chosen to be much larger due to factors such as the space that can be taken around the furnace, but the benefits of a larger diameter increase proportionally with the diameter, as described above. Not the thing, the actual maximum diameter is 75 cm (30 inches) and the cross-sectional area is 4,417 cm ²
(707 square inches). As mentioned above, the cross-sectional area of the nozzle of the preferred embodiment is 35 cm ² (5.0 square inches), so the ratio of these two areas is 1:
It turns out to be 90. Practical minimum and maximum dimensions of the nozzle are 3.8 cm (1.5 inches) and 10.0 cm, respectively
(4 inches) and the corresponding cross-sectional area is about 1 each
It will be 1.3 cm ² (1.77 square inches) and 79 cm ² (12.5 square inches). A practical range for the ratio of the two areas is 1:50 to 1: 250, preferably 1:60 to 1: 150. These large ratios are in stark contrast to most of the prior art values of 1: 1 and 1:16 in the device of US Pat. No. 4,008,884.

With such a large volume and cross-sectional area of the reservoir, a large amount of metal can be moved at a high velocity,
Therefore, the total momentum can be increased, the mixing speed can be increased, and the cycle time can be relatively lengthened. This feature allows for more predictable control because it increases the time available to initiate and identify each part of the cycle.

The relatively short, large-diameter reservoir, which is a feature of the present invention, has a horizontal inner diameter of the inner chamber containing the molten metal and a normal upper level.
It can also be defined by the ratio between the vertical distance from 92 to the normal lower level 94. In this example, the diameter is 60 cm (24 inches) and the vertical distance is about 90 cm (36 inches), so the ratio is 1.50: 1. The practical range of values for this ratio is about 1.0: 1 to 2.0: 1.

Yet another feature is the ratio of the horizontal cross-sectional area of the interior chamber to the vertical distance between levels 92 and 94, which is greater than about 25 cm ² / cm (10 square inches / inch). Is preferred.

The use of a flow restricting nozzle has the advantage, as described above, of forming a metal-entrained high-speed jet that performs the required range of functions.
Appropriate selection of the nozzle size, nozzle position and jet entry angle allows the resulting mixing action to be exerted throughout the bath, yet such action is achieved despite the high velocity of the incoming metal. , Without any noticeable disturbance of the metallic surface of the bath. The use of smaller diameter nozzles requires a higher pressure in the reservoir to provide the necessary metal evacuation.

The flow restricting nozzle also favors the flow of metal into the interior of the sump. In particular, as shown in FIG. 6, directing a jet of incoming metal tangentially to the horizontal circular cross section inside the reservoir has a positive effect. The general shape of such a flow found in a horizontal cross section is indicated by arrow 110 in FIG. The rapid vortices thus generated in the incoming metal reduce the formation of dross, and since the upper portion of the inner wall is kept at a high temperature by the adjacent heater 78, the adhesion to the upper portion of the inner wall can be reduced. Dust, which is usually in the shape of a body, accumulates at the locations indicated by dotted lines 112 and 114 in FIG.
In the case of a reservoir of square or rectangular cross section, no such vortex effect is obtained and the deposit 114 on the side directly opposite the side on which the incoming jet strikes is much faster than on the other side. You can see that it grows. The relatively small diameter tubes of the prior art devices do not allow the advantageous scouring action obtained in a cylindrical reservoir to be adequate.

In practice, the formation of a plaque ring just below the upper level 92 is unavoidable, but in the present invention such an adverse effect is substantially mitigated due to the relatively large inner diameter. Thus, it is quite common for dirt to deposit at a high rate of 3 kg (6.6 lbs) / hour, and prior art thin tubes stop stirring at intervals of 5-7 hours to scrape the ring. It will have to be done. Even though the thin prior art tubing does not impede the flow, it can cause significant problems by contacting the upper level control electrodes and short-circuiting them, thus preventing effective control until the ring is removed. Become. It takes about 5 to 10 days before such adhesion becomes a serious problem in the apparatus of the present invention, and the cleaning operation itself can be performed in only about half an hour. The time before sticking becomes a significant issue can be significantly lengthened by the heater safely attached to the cover. Inside the reservoir, where the cover can be removed and easily accessed, hot and soft,
Removing the ring, which can be easily separated, is relatively simple.

The electrical system is shown schematically in FIG. The level electrodes 86, 88 and 90 and the load cell 30 (if provided) are controlled by a system controller 116, which comprises a programmable logic controller (PLC), which controls the heater 78 and the jack 50. It controls a power control device 118 that controls the supply of electric power obtained from the three-phase transformer to the motor 51. The system controller is also distributed in a known manner to control the pneumatic systems 122, 124 for agitation operations and to provide visual instructions and permanent records regarding these operations.

Although the pneumatic system is shown as one block 122, 124 in FIG. 9 for convenience, a typical pneumatic system is shown schematically in FIG. In practice, the system 122 is attached to the cover and the system 124 is attached along the sump, the two systems being connected by a flexible high pressure metal hose so that the cover can be removed as described above. ing. In the present embodiment, the vacuum is obtained by the ejector 126, but with such a configuration, the vacuum is obtained by the action of the compressed air that provides a positive pressure, so that the cost can be reduced and the structure can be simplified. it can. The ejector is directly connected to the flange 106 of the cover. Compressed air is supplied to the injector from a suitable compressor pump (not shown) via pipe 128, and the injector throat is provided by a nozzle sized to deliver the air pressure used.
Directed to. The air pressure can be varied from about 1.05 to 5.6 kg / cm ² (15 to 80 psi), with a 7.5 cm ejector 1.4 kg / cm ² (20 psi) to 4.2 kg / cm ² (60 p
si) pressure was used successfully. This air is
It is passed through a colloidal filter with automatic drainage, where water is removed and not returned to the pump, and then reaches the nozzle 130 via a solenoid controlled drain valve 134 and a large volume main pressure control valve 138. . The ejector outlet is a piston operated butterfly valve 140
Is opened and closed under the control of the system controller 116.
Valve 140 is a solenoid operated actuator valve 1
Actuated by piston actuator 142 under control of 44. When the butterfly valve 140 is opened, it acts like a jet pump (jet pump), and compressed air from the nozzle forms a vacuum through the outlet 106, and when it is closed, a positive pressure is generated. Noise at the time of ejecting the ejector is reduced as much as possible by the muffler 146. By using the smallest piston actuator 142 with an oversized actuator valve 144, the opening and closing speed of the butterfly valve can be less than 0.025 seconds. By opening and closing in such a short time, the reversal movement of the metal can be performed quickly and stably, and high frequency circulation can be performed by only one moving portion in the air flow.

The air pressure required for the positive pressure portion of the cycle is much lower than the pressure required to create the vacuum, and the required pressure is applied when required by actuation of the regulator valve 138. The low pressure value for the pressurization mode is set by the regulating valve 148 and the high pressure value for the exhaust mode is the regulating valve.
Set by 150 and both are obtained by working air supplied from line 128 via regulating valve 152. The valve 152 stabilizes the pressure of this air to compensate for variations in the toes caused by operation of the system. valve
The 148 is also feedback controlled using the internal pressure of the reservoir obtained from the outlet 102 so that the response and pressurization is significantly faster and the reversal movement of the metal is within a few millimeters during pressure reversal. Done in. Excessive pressure at outlet 102 is indicated by diaphragm switch 153. The pilot pressure supplied to valve 138 to cause valve 138 to apply the required pressure at nozzle 130 is selected by a four-way solenoid operated valve 154, and air is now required to shut off the regulating valve for safety. In any case, it is supplied through a solenoid-operated shutoff valve 156 capable of such actuation. Furthermore,
For safety purposes, the exhaust valve 134 can be activated so that the line 128 can be connected to the atmosphere via the muffler 158 to completely shut off the supply of air to the ejector. When the valve 144 is de-energized,
By quickly energizing the butterfly valve to the open state, the valve can already open before the compressed air supply is shut off. Thus, the interior of the reservoir can be connected to the atmosphere so that the liquid level can be gravity lowered to level 98. These emergency shut-off mechanisms are activated, for example, when the electrodes detect too high levels of metal, when overpressure at outlet 102 is detected, or when the operator presses the emergency button. An independent safety device, which is independent of the system control device when an overpressure occurs, is constituted by a rupture disc 160 provided on the ejector.

Alternatively, the main pressure adjusting valve 138 is set to an appropriate current −
Current-to-pressure pilote c
can be programmed directly from the system controller 116 using a programmable logic controller operated via an onverer).

Precise level control between the lowest and highest levels is important for satisfactory operation, increasing the cross-sectional area of the sump (about 14 times greater than prior art systems). This makes this easier,
More accurate control can be performed. This is because the vertical movement of the metal becomes slow, and it becomes easier to predict the operation and control of the inertial component of large momentum. In operation in a mode in which the reservoir is filled until electrodes 86, 88 indicate that level 92 has been reached, the system will
Electrode life can be extended by responding to an upper level signal just below the level already indicated to prevent molten metal from contacting the electrode for a predetermined number of cycles. The system can be configured so that the electrodes are contacted with the metal once every 10 to 15 minutes to allow the system to function properly.

Although it is more difficult to accurately control the upper level, such control can be advantageously performed by measuring when the level is below the top of the passage section 66, which allows the exhaust gas to reach the furnace. To form bubbles in the. The generation and movement of gas bubbles can be detected by a pressure turbulence monitor of suitable sensitivity and cause a small, easily detectable variation in the signal obtained from the monitor, a small oscillation of the internal gas pressure. Occurs in response to. The detection of this signal can be used for automatic lower level correction by shortening the expulsion phase.

An example of the operating mode of this control system is shown in FIG. When started, the suction phase will be slightly shorter T
Starting from ₁ and then the emission phase corresponds to a short period T ₂
Performed in. Both of these periods end without detecting a signal indicating whether the reservoir is fully filled or empty. Subsequent corresponding period T ₃
And T ₄ is somewhat longer. Extreme limi
t) If the signal is not yet obtained, these periods are increased again, indicating that at the end of the suction period T ₅ the electrodes 86, 88 have reached the upper level, the subsequent suction period is substantially A little shorter, for example 10 to 15 minutes,
Increase again until upper level detection is done. Similarly, at the end of infusion period T ₆ or at the beginning of period T ₇ ,
When the pressure turbulence monitor indicates that bubbling has occurred,
Subsequent periods are shortened by substantially the same amount of time. This cycle is repeated as long as a substantial amount of time is deemed appropriate. Thus, the system dynamically adjusts itself to maximize the volume of metal expelled during each actuation cycle while minimizing foaming.

An example of a suitable pressure turbulence monitor is shown in FIG. 12 and is generally designated by reference numeral 162 in FIG. A small, constant flow rate of air obtained from the regulating valve 152 allows a constant differential pressure control system 164 [eg Moore Instrument Model 63BDL (Moore In-stru
ment Model 63 BDL)] and adjustable needle valve 166
Through a transparent rotameter 168 [Matheson 7262 (Mathe
son 7262)]. The rotameter consists of lower and upper rebound springs 170 and 172 and lower and upper infrared position detectors 174 and 176 [eg SCAN-A-MATIC MODEL P-L34024 (SKAN-A-MATIC MODEL
PL 34024)] and the
Monitor the position of float 178 along the rotameter tube. The outlet of the rotameter is connected to a pipe leading to the outlet 102 and is adapted to return a small amount of air via pipe 180 to the controller 164 for conditioning.

The needle valve 166 is adjusted to create a desired flow rate (eg, 0.75SCFH) that just cuts the beam provided by the lower position sensing device 174 while the pump pressure remains stable or without any turbulence. . If bubbling is obtained towards the end of the pressurization cycle and its initiation causes a sudden and very small pressure drop in the air supply line, it will change too fast to be compensated by the controller 164. A corresponding "fly" of float occurs in the tube. This jump is sufficient for the float to cut the beam of the upper detector 176, which provides an input to the system controller 116 to quickly switch the cycle from pressurization to suction. The device of the present invention is sufficiently quick and sensitive that it can limit foaming to one small bubble and yet have low inertia so that the float can respond to pressure changes in milliseconds. Recognize.

The device of the invention can also be used to monitor the cycle of the pump electrically in the system and visually by monitoring the movement of the foot.
Thus, each pressure reversal results in a significantly strong float movement sufficient for the float to engage its respective hold down spring. For example, when the system is in pressure mode with steady pressure, reversal to vacuum mode causes the float to move up through the beam of the upper position detector 176 and back into engagement with the spring 172. Also, the reversal from vacuum mode to pressurization mode causes the float to move downward from the beam of lower detector 174 and back again. The system controller detects the resulting sequence of signals and uses this as a positive means to monitor the proper operation of the ejector. If the correct signal from the monitor is missing, the operation is stopped. Also, such signal loss is particularly useful for detecting any pressure perturbations caused by, for example, some improper actuation of butterfly valve 140 or destruction of disk 160.

Alternatively, the pneumatic type control system 164 can be replaced by a pressure to current converter that receives a feedback signal (dotted line) from the system controller 116, which feedback signal is used as a position control output signal for the lower level detector 174. Obtained from

The use of an ejector to obtain a suitable vacuum is simple and reliable, but somewhat unsatisfactory. A blower is preferably used when an appropriate compressed air source is not available, and an example of an appropriate system is shown in FIG. A blower 18 of appropriate size to operate in either vacuum or pressure mode under the control of a spool valve 184 operated by a double-acting piston 186 moving in a cylinder 188 under the control of a solenoid operated valve 190.
Two can be arranged. The blower assembly is connected to the inlet 106 of the cover 32 by a special pipe 192, which has a larger internal volume than the amount of air withdrawn in vacuum mode when the metal moves between the lowest and highest levels. Should be long enough and have a sufficiently large diameter so as to prevent the heated air from reaching the blower from the inside of the reservoir and heating the blower. For this reason, the pipe 192 should be able to radiate a large amount of heat at the end closest to the blower, for example, by providing a radial radiating blade 193. With this structure, the hot air removed from the reservoir in the exhaust mode is forcibly returned to the reservoir, and the air can suppress cooling of the reservoir wall.

A butterfly valve 194 operated by a motor 196 under the control of a solenoid operated valve 198 constitutes a start and heat release valve. During start-up, the valve is opened and the blower motor is accelerated to operating speed and then closed in both vacuum and pressure modes. Thermostat 200 detects the temperature of the air near the blower and if the temperature is too high, valve 194 is opened to cool the system. The valve closes when it reaches a sufficiently low temperature. Mufflers 202 and 204 are provided to reduce system noise, and air entering the system passes through a filter 206. Due to the closed loop operation, such a system provides high pneumatic efficiency and low heat loss. Being a closed loop, the system can reduce the formation of dross by injecting an inert gas through the inlet 208 and valve 210 to replace as much air in the system as possible.

A metering device consisting of the load cell 30 can be used for level detection and foam generation detection. This device
It is intended to support the reservoir and to measure different loads on the reservoir when the reservoir is filled to different levels 92, 94 and 96. These loads produce a corresponding signal that is proportional to the corresponding weight of the reservoir and can be used directly for level control. Thus, the cell can be used for calibration or can be used to determine if the lower level controller has dropped to an abnormally low level. Bubble formation and movement in the reservoir produces a corresponding small oscillation of the reservoir that can be detected by the load cell and produces an easily detected signal indicating that the drain phase should be shortened.

(Effect) As described above, according to the stirrer of the present invention, stirring can be performed sufficiently efficiently, and installation cost and maintenance cost can be reduced.

[Brief description of drawings]

FIG. 1 is a horizontal cross-sectional view of a rectangular plane melting or casting furnace showing a typical arrangement of the stirring device with respect to the inside of the furnace, and FIG. 2 is a side view of the stirring device seen from the direction of arrow 2 in FIG. Fig. 3 is a plan view seen from the direction of arrow 3 in Fig. 2, Fig. 4 is a vertical sectional view taken along line 4-4 of Fig. 3 including a joint portion of a furnace, and Fig. 5 is an arrangement of heating elements. 5 in FIG. 4 showing examples, etc.
5 is a sectional view taken along line 5-6, and FIG. 6 is a horizontal sectional view taken along line 6-6 of FIG. 4 showing the arrangement of outlet nozzles including a connection portion of the furnace wall, and FIG. 7 is a sectional view taken along line 7-7 of FIG. FIG. 8A is a graph showing the relationship between time inside the reservoir and pressure value, FIG. 8B is a graph showing the relationship between time inside the reservoir and metal level, and FIG. 9 is an electrical diagram of the device of the present invention. FIG. 10 is a schematic diagram showing the layout, FIG. 10 is a schematic diagram showing the pneumatic circuit of the device of the present invention, and FIG. 11 is a graph diagram showing the novel method of upper and lower level control used in the present invention. FIG. 12 is a schematic diagram showing a pressure turbulence monitor used for detecting bubble generation and pressure reversal inside the reservoir, and FIG. 13 is a schematic diagram showing another vacuum / pressure supply means of the present invention. . 10 ... Furnace, 12 ... Hearth, 14, 16 ... End wall, 18, 20 ... Side wall, 22
... inspection door, 24 ... loading door, 26 ... stirring device, 27 ... nozzle part, 30 ... load cell, 32 ... cover member, 34,36 ... flange, 38 ... bolt, 40 ... bracket, 42 ... rod, 44 ... bush, 46, 48 ... arrow, 50 ... jack, 51 ... electric motor, 52
... outer lining, 54 ... middle lining, 56 ... inner lining, 58, 60 ... flange, 62 ... bolt, 64 ... block, 66 ... passage part, 68 ... nozzle opening, 70 ... passage part, 74
… Thermostat, 76… Central space, 78… Heater, 80… Case, 82… Cover, 84… Shield, 86, 88, 90… Electrode,
92 ... upper level, 94 ... lower level, 96 ... level, 98 ... flat level, 100 ... observation port, 102 ... pilot pressure connection, 10
4 ... hole, 106 ... pipe, 180 ... hole, 116 ... system controller, 118 ... power controller, 120 ... transformer, 122,124 ... pneumatic system, 126 ... ejector, 128 ... pipe, 130 ... nozzle, 132 ... Filter, 134 ... Discharge valve, 138 ... Pressure adjusting valve, 140 ... Butterfly valve, 142 ... Piston actuator, 144 ... Actuator valve, 146 ... Muffler,
148, 150, 152 ... Regulator valve, 153 ... Diaphragm switch, 154 ... Solenoid operated valve, 156 ... Shutoff valve, 15
8 ... Muffler, 160 ... Bursting disc, 162 ... Pressure disturbance monitor, 164 ...
Constant differential pressure control system, 166 ... Niddle valve, 168 ... Rotameter, 170, 172 ... Spring, 174, 176 ... Position detection device,
178 ... Float, 182 ... Blower, 184 ... Spool valve, 1
86 ... Double acting piston, 188 ... Cylinder, 190 ... Solenoid operated valve, 192 ... Pipe, 194 ... Butterfly valve, 196
… Motor, 198… Solenoid operated valve, 200… Thermostat, 202, 204… Muffler, 206… Filter, 208… Inlet, 210… Valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Andre Gendron, Mocha Street 2496, John Quayère, G.7S, Quebec, Canada 2496 (72) Inventor Marc Oger Canada Quebec, G7S, 3X7, John Quayers, Guilome Street 2401

Claims (23)

[Claims] 1. A molten metal stirrer for stirring molten metal in a furnace chamber, wherein a reservoir chamber separated from the furnace chamber is communicated with the inside of the chamber and the molten metal is passed between them. Alternative and continuous formation of a passage and a vacuum for drawing molten metal from the furnace chamber into the interior of the reservoir and a positive pressure for discharging molten metal from the reservoir chamber to the furnace chamber in the form of a stirring jet. And a vacuum / pressure generating means connected to the inside of the sump chamber, the molten metal is drawn into the sump chamber until it reaches the upper level in the sump chamber, and is discharged until it reaches the lower level. The ratio of the diameter of the horizontal cross section inside the reservoir chamber to the vertical distance between the upper and lower levels is about 1.0: 1 to 2.
Molten metal stirring device characterized by being 0: 1. 2. A horizontal cross section of the interior of the reservoir chamber is substantially circular, and the passage extends horizontally from the reservoir chamber side in the opening direction.
Moreover, the molten metal agitating device according to claim 1, wherein the molten metal agitating device is opened on the side of the storage chamber in a tangential direction with respect to the circular cross section. 3. The passage is provided with a nozzle, and the ratio of the cross-sectional area of the nozzle to the horizontal cross-sectional area of the inside of the reservoir chamber is 1:50 to 1 :.
The molten metal agitator according to claim 1 or 2, wherein the molten metal agitator is in the range of 250. 4. The molten metal agitator according to claim 3, wherein the ratio is 1:60 to 1: 150. 5. The sump chamber is mounted on a weighing device for measuring the weight of the sump chamber so as to measure the level of molten metal in the sump chamber. The molten metal stirring device according to the item. 6. The molten metal agitator according to claim 5, wherein the sump chamber is mounted on a load cell for measuring the weight of the sump chamber so as to measure the level of the molten metal in the sump chamber. . 7. The reservoir chamber is a weighing device for measuring the weight of the reservoir chamber so as to detect a change in the reservoir chamber due to bubbling of a pressurized gas introduced into the furnace from the inside of the reservoir chamber through a passage. The molten metal stirring device according to claim 5 or 6, which is mounted. 8. The reservoir chamber is provided with a removable cover part so that the inside of the chamber can be accessed, and the cover part is provided with a heating means for heating the inside of the reservoir chamber and the molten metal. The molten metal stirring device according to any one of claims 1 to 7, characterized in that. 9. A means for attaching the cover part so that the cover part can be moved in the vertical direction with respect to the remaining part of the reservoir to separate the cover part from the remaining part. Item 9. A molten metal stirring device according to item 8. 10. The removable cover portion further comprises a level control electrode extending into the interior of the reservoir chamber for measuring an upper level of molten metal within the reservoir chamber. Stirrer. 11. The melting apparatus according to claim 8, wherein the removable cover portion is provided with means for forming a vacuum in the reservoir chamber and supplying gas under pressure. Metal stirrer. 12. A pressure detector for detecting a pressure fluctuation in the reservoir chamber caused by bubbling of a pressurized gas introduced into the furnace from the reservoir chamber.
The stirring device according to any one of 11 above. 13. The pressure detector comprises a rotor meter through which a constant flow of air passes, and the air is supplied to the inside of the reservoir chamber and the flow of air passing through the rotor meter is affected by pressure fluctuations inside the reservoir chamber caused by bubbling. 13. The molten metal stirring device according to claim 12, wherein: 14. The rotameter comprises a float device placed in a constant flow of air which is disturbed by pressure fluctuations whose level is detected, and the pressure detector comprises a float device from a parallel position corresponding to a steady pressure inside the reservoir chamber. 14. The molten metal stirring device according to claim 13, further comprising means for detecting movement. 15. The signal from the pressure detector according to claim 14, wherein the signal from the pressure detector is used to shorten the time that the positive pressure is accumulated and applied to the inside of the chamber when the detector detects the foaming. Molten metal agitator. 16. The vacuum / pressure generating means comprises a butterfly valve for periodically switching between vacuum and positive pressure,
The butterfly valve is operated on an output from a programmable logic controller, the programmable logic controller comprising:
16. A means for automatically adjusting the cycle according to the outputs of a level control electrode for detecting the upper level of the molten metal and a pressure detector for detecting the bubbling. The molten metal stirring device according to the item. 17. The cycle is automatically adjusted such that the level control electrode detects the upper level once per cycle and the bubble detection by the pressure detector is less than once. 17. The molten metal stirring device according to claim 16, wherein: 18. The passage is provided so as to form an angle of 10 to 45 degrees with respect to a surface of the open end on one side of the furnace adjacent to one end or an open end of the furnace adjacent to the one side. The molten metal stirring apparatus according to any one of claims 1 to 17, characterized in that 19. The vacuum / pressure generating means comprises an ejector having a low pressure inlet connected to the inside of the reservoir chamber and a high pressure inlet connected to a high pressure air source, the ejector being at the inlet via the low pressure inlet to the reservoir chamber. 19. A butterfly valve having a butterfly valve which is opened for applying a vacuum inside and closed for applying high pressure air inside the reservoir chamber via a low pressure inlet. The molten metal stirring device according to the item. 20. A pressure regulating valve controlled by the programmable logic controller based on the cycle,
The high pressure air applied to the high pressure inlet of the ejector was supplied by the pressure regulating valve, the pressure of which increased to a high value when the butterfly valve opened, the butterfly valve closed and the pressure was applied inside the reservoir chamber. 20. Molten metal stirring device according to claim 19, characterized in that it sometimes decreases to a low value. 21. Selectively and continuously a vacuum for drawing molten metal from the furnace chamber into the interior of the reservoir chamber and a positive pressure for releasing molten metal from the reservoir chamber to the furnace chamber in the form of a stirring jet. A vacuum / pressure generating means connected to the inside of the reservoir so as to form a blower having an inlet and an outlet, and the inlet and the outlet selectively inside the reservoir. A means for selectively applying a vacuum and a pressure to the inside of the reservoir connected to the reservoir.
19. The molten metal stirring device according to any one of claims 18 to 18. 22. A pipe is provided for connecting a blower to the inside of the reservoir, the internal volume of the pipe being at least equal to the volume of gas pumped between a minimum metal level and a maximum metal level, during a vacuum cycle. 22. The molten metal stirring device according to claim 21, wherein the gas removed from the inside of the storage chamber is stored in the pipe and is returned to the inside of the storage chamber during the pressure cycle. 23. The molten metal agitator according to claim 21, further comprising means for injecting an inert gas into the interior of the reservoir to discharge the atmosphere in the reservoir.